The present invention relates to an ultraviolet/infrared absorbent low transmittance glass. More particularly, it relates to an ultraviolet/infrared absorbent low transmittance glass which has an almost neutral color such as turquoise blue shade and deep green shade so that it is useful for windows of vehicles or buildings when used in combination with a glass having green shade with high visible light transmittance, and which has low or middle visible light transmittance, low total solar energy transmittance, and low ultraviolet transmittance so that it is suitable for use as privacy glazing in a vehicle.
Recently, a variety of glasses with ultraviolet/infrared absorbability to be used as a vehicle windshield have been proposed with the view of preventing degradation of luxurious interior materials and reducing cooling load of the vehicle. In view of privacy protection, glass with relatively low visible light transmittance is preferably used for a rear window glass of a vehicle. Such kinds of glass include the followings.
For example, a dark gray colored infrared absorbent glass disclosed in Japanese Patent Publication No. 7-29813 consists of soda-lime-silica glass including colorants consisting of 1.00 to 1.7 weight percent, Fe2O3 (total iron), at least 0.27 weight percent FeO, 0.002 to 0.005 weight percent Se, and 0.01 to 0.02 weight percent CoO. The glass exhibits luminous transmittance less than 32 percent and total solar infrared transmittance less than 15 percent at 3.9 mm thickness.
A dark gray colored glass disclosed in Japanese Unexamined Published Patent Application No. 8-157232 consists of soda-lime-silica glass including colorants consisting of 0.8 to 1.4 weight percent Fe2O3 (total iron), less than 0.21 weight percent FeO, 0.05 to 1.0 weight percent TiO2, 0.02 to 0.05 weight percent CoO, and 0.0005 to 0.015 weight percent Se.
A neutral gray colored glass disclosed in claim 25 of U.S. Pat. No. 5,393,593 has a base glass composition comprising 66 to 75 weight percent SiO2, 10 to 20 weight percent Na2O, 5 to 15 weight percent CaO, 0 to 5 weight percent MgO, 0 to 5 weight percent Al2O3, and 0 to 5 weight percent K2O, and colorants consisting of 1.00 to 2.2 weight percent Fe2O3 (total iron), at least 0.20 weight percent FeO, 0.0005 to 0.005 weight percent Se, and 0.010 to 0.030 weight percent CoO. The glass exhibits luminous transmittance less than 35 percent and total solar infrared transmittance less than 20 percent at 3.9 mm thickness.
A soda-lime-silica glass disclosed in Japanese Publication of PCT No. 8-506314 has a neutral color by including primary iron given by the following expression:FeO (weight percent)≧0.007+(optical concentration−0.036)/2.3and 0.25 to 1.75 weight percent Fe2O3 and at least one selected from a group consisting of Se, Co3O4, Nd2O3, NiO, MnO, V2O5, CeO2, TiO2, CuO, and SnO. The glass exhibits luminous transmittance more than 32 percent, ultraviolet transmittance less than 25 percent, direct solar energy transmittance at least 7 percent less than the luminous transmittance, and dominant wavelengths preferably less than 570 nanometers at 4 mm thickness. Certain embodiments thereof may be used as a privacy glazing.
In both the dark gray colored infrared absorbent glass disclosed in Japanese Patent Publication No. 7-29813 and the dark gray colored glass disclosed in Japanese Unexamined Published Patent Application No. 8-157232, a great quantity of Se is used for providing a desirable color. Such a great quantity of Se is unpreferable for the environment because Se has toxicity and is easy to vaporize. The above dark gray glass including 0.05 to 1.0 weight percent TiO2 as an essential component is unpreferable because TiO2 is expensive to increase the batch cost.
The neutral gray colored glass disclosed in U.S. Pat. No. 5,393,593 is also unpreferable because of the great content of Se. The great content of FeO is preferable in view of heat ray absorptivity, FeO is on the contrary not preferable because it selectively absorbs infrared ray in a wavelength from 1,000 to 1,200 nanometers so that in case the glass is produced by a normal melting furnace, it absorbs most efficient portion in flame luminance distribution so as to lower the temperature of bottom base of the furnace and then contribute to various defects.
Though the aforementioned glass with low visible light transmittance is superior in view of privacy protection, an occupant in a vehicle cabin sees outside quite unclearly through the glass. On the other hand, a glass with middle transmittance can be sufficient to some extent for both privacy protection and safety. These types of glass are chosen according to portions in a vehicle and circumferences.
The aforementioned glass includes selenium in high concentration to provide optical properties, without essentially including nickel.
The glass of Japanese Publication PCT No. 8-506314, which can be used for privacy protection, is provided with a neutral color by including colorants consisting all of nickel, selenium, and cobalt, just as described in this specification. However, it is necessary to add a great quantity of Se since the content of nickel is low.